1. Field of the Invention
This invention relates to an apparatus for making a yarn, comprising defibrating means for defibrating at least one fibrous roving, two juxtaposed, closely spaced twisting drums, which succeed the defibrating means and define a generally triangular twisting space, to which suction is applied, and withdrawing means, which axially succeed the twisting drums and serve to withdraw the twisted yarn made from the singled fibers in said twisting space.
2. Description of the Prior Art
A desirable spinning operation can be performed in a generally triangular twisting space between two closely spaced twisting drums, which are rotated in the same sense and exert a suction adjacent to the line of yarn formation. For that operation the singled fibers to be spun must be delivered to the twisting space in such a manner that the fibers can be twisted to form a yarn. For that purpose it is known to throw off the singled fibers from the serrated defibrating cylinder of defibrating means into the twisting space although the fibers cannot be aligned in that case. In that connection it must be taken into account that for a uniform twisting of the fibers it is desired that the fibers are parallel to each other and desirably extend in the direction of the line of yarn formation. For this reason it has been suggested to provide between the defibrating means and the twisting space a fiber-guiding passage, which is inclined by a small angle from the line of yarn formation and which will be affected by the suction stream flowing through the suction zones of the twisting drums so that an entraining air stream will be produced within the fiber-guiding passage and will align the fibers in the longitudinal direction of the passage. That known delivery of the fibers to the twisting space has the disadvantage that owing to the high velocity at which the fibers are conveyed the fibers are upset as they impinge on the fibers which have been joined in the yarn being formed and such upsetting will necessarily result in irregularities so that the strength of the yarn which can be achieved will be reduced.
It has been proposed (EP-A-175 862) to avoid said disadvantages in that the fiber-guiding passage is directed toward that twisting drum which rotates toward the twisting space, the yarn is withdrawn from the twisting space opposite to the feeding direction of the fiber-guiding passage, and the velocity of flow of the entraining air in the fiber-guiding passage is selected to be at a certain ratio to the peripheral velocity of the twisting drums. But these measures do not permit high-strength yarns to be spun under conditions in which the requirements for the twisting of the yarn are taken into account.